Nec Corporation

Yukio Miyamoto

Kiyokazu Okamoto

Hiroshi Iijima

Yoshiharu Suzuki

Stator slots are skewed relative to rotor slots with a skew amount comprising an integer multiple of a stator electrical angle of 60.degree., thereby minimizing a torque ripple which is an integer multiple of six times of a primary frequency of electrical energy.

Induction motor

A three-phase induction motor is subjected to countermeasure for the rotor and the stator in order to remove two harmonic components of the orders causing a torque ripple, among a plurality of harmonic components included in a magnetic flux generated in an air gap between a stator core and a rotor core. In the three-phase induction motor, conductor grooves of the rotor core are skewed by an electrical angle of 2.pi./n where n is the order of one of the harmonic components to be removed. In the stator, the number of slots (N) is selected so that an equation N=l.times.m.times.q is satisfied, where l=the number of poles, m=the number of phase, and q is a non integer number representing the number of slots per pole per phase, and the stator winding pitch is determined according to the order of another harmonic component to be removed.

Three-phase induction motor

A three-phase induction motor includes winding slots and a stator winding. The number of winding slots per pole per phase is a noninteger. The stator winding is a three-phase balanced winding. A pitch s of the winding satisfies s=(r-t)/r or s=r/(r+t) (where t is an odd number and r is the order of a harmonic wave to be suppressed).

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Tokyo, Japan

Yukio Miyamoto